Psychrometer with air circulating means



: p 7, 1954 .1. F. KING, JR

PSYCHROMETER WITH AIR CIRCULATING MEANS Filed Sept. 22, 1950 Gttomegs.

Patented Sept. 7, 1954 PSYCHROMETER WITH AIR CIRCULATIN G MEANS James F.King, Jr., Winston-Salem, N. (3., assignor to The Bahnson Company,Winston- Salem, N. 0., a corporation of North Carolina ApplicationSeptember 22, 1950, Serial No. 186,293

4 Claims.

This invention relates to motorized psychrometers and more particularlyto psychrometers including wet and dry bulb thermometers over which anair stream is established by a fan or blower.

Objects of the invention are to provide a motorized psychrometer in thegeneralform of an elongated rod or tube supporting a wet bulb and a drybulb thermometer, batteries, and a miniature motor and fan forestablishing an air current over the thermometers, and an adjustablecomputer for determining the relative humidity from the observed wet anddry bulb temperatures. An object is to provide a psychrometer of thetype stated which includes a signal system for displaying a significantsignal when the batteries are of low voltage and should be replaced.

These and other objects and the advantages of the invention will beapparent from the following specification when taken with theaccompanying drawings in which:

Fig. 1 is a side elevation of a motorized psychrometer embodying theinvention;

Fig. 2 is a top plan view of the same;

Fig. 3 is a fragmentary central vertical section on a larger scale andshowing the motor and fan assembly separated from the supportingstructure;

Fig. 4 is a transverse vertical section on line 4-4 of Fig. 1;

Fig. 5 is a transverse vertical section on line Fig. 6 is a transversevertical section on line 6-6 of Fig. 1; and

Fig. 7 is a fragmentary central vertical section through the outer endof the psychrometer.

In the drawings, the reference numeral I identifies the tubular rear endor handle portion of an elongated support which is preferablyformed bycutting approximately semi-cylindrical sections from a stainless steeltube. A relatively short section is removed from the intermediateportion of the tube to' leave a semi-cylindrical section 2 to which acomplementary semi-cylindrical plate 3 is detachably secured, as will beexplained later, and a longer section is removed from the opposite sideof the outer end of the tube to leave an outer section 4 of somewhatmore than semi-cylindrical form which is spaced from the section 3 by ashort section 5 of full cylindrical form. In general, the functions ofthe several parts of the elongated support are as follows: the tubularrear portion I constitutes a handle for carrying the psychrometer andholding it in spaces where humidity measurements are to be made, andalso serves as a container for a battery of dry cells; the intermediatesection 2 and the complementary plate 3 form a housing for a miniatureelectric motor and fan which are mounted on the plate 3; the outersection 4 provides the support for wet and dry bulb thermometers; andthe section 5 constitutes a yoke within which the thermometer bulbs arelocated in the path of the air stream established by the fan.

A removable cap 6 closes the rear end of the handle portion I andcarries a spring I which engages the zinc can electrode of the adjacentdry cell 8 of a battery, preferably three cellsof conventionalflashlight type, within the handle portion I which is of a diameter tobe conveniently grasped in the hand in the same manner as a flashlight.An insulating disk 9 is secured across the forward end of the tubularportion I of the support, and a conductive pin I0 extends axiallythrough the disk for engagement by the center contact of the forward drycell 8 and a cooperating spring contact I I of the motorfan assemblysupported upon the plate 3.

This assembly includes a switch I2 having one terminal to which thespring contact II is secured, and a second terminal from which leads I3,I4 extend in parallel to a miniature electric motor I5 and to oneterminal of a lamp socket I 6 in which a signal lamp I1 is seated. Theother side of the motor is grounded upon the support by a lead I 8, andthe second terminal of the lamp socket It has a contact strip I9soldered thereto for cooperation with a grounded spring contact 26 whichis normally biased away from the contact I9, but is forced into contactwith it by a centrifugal governor 2| on the motor shaft when the batteryvoltage drops below that value which afiords stable motor operation fora preselected time interval, say 30 seconds, sufficient to bring the wetand dry bulb thermometers to stable minimum readings. A red glass lensor bullseye 22 is mounted in an opening in the part 2 to afford a clearindication to the operator when the motor speed drops below apreselected value due to depletion of the battery of dry cells B.

The motor I 5 has a snug fit within a mounting ring 23 which is securedto the plate 3 by screws 24, and a fan or centrifugal blower 25 ismounted upon the outer end of the motor shaft. A series of exhaustopenings 26 are provided in the support section 2 and the mounting plate3, and a pair of slots 26' are provided in the section 2 to establish anair stream for cooling the motor. The plate 3 and its assembly. aredetachably 3 secured to the support section 2 by screws 21 which arethreaded into the ring 23.

The wet bulb thermometer W and the dry bulb thermometer D are mountedupon a subbase of generally cruciform cross-section comprising a strip28 which, for convenience of description, will be termed the verticalstrip, and a pair of horizontal strips 29, 29 which are welded to theopposite sides of strips 28 below the center line thereof. Thethermometers are mounted upon the respective strips 29' by clips 30, andthe strips 29 terminate short of the thermometer bulb to avoidinterference with the air flow around the bulbs. The lower portion ofthe strip 28 is notched, well in advance of the thermometer bulbs, toreceive the water tank 3| which is welded or soldered to the lower facesof the strips 29. The lower surface of the water tank is curved to fitsnugly against the adjacent wall of the support section 4, and the tankfiller cap 32 extends through an opening in that wall to close thefiller opening and also to lock the sub-base securely to the support. Alinen wick 33 on the bulb of the thermometer W passes into the tankthrough a rubber bushing 34 which is tightly compressed upon the wick toprevent leakage from the tank. The rearward end of the vertical plate 28fits snugly within the support section when the sub-base is slipped intothe outer support section i, and a cap 35 is welded to the outer end ofthe sub-base to seat upon the outer end of section A with a snug fit.

At least the rear portion of the metal sub-base which is exposed to theair stream is covered or coated with heat insulating material, indicatedby the stippling 36, and. the interior of the support section is alsolined with insulating material 37 to reduce heat transfer from thesupporting structure to the thermometer bulbs.

A computer or rotary slide rule for determining relative humidity fromthe observed wet and dry bulb temperatures is mounted upon the outerportion of the handle section I. The computer comprises a ring 38press-fitted upon the handle i and marked with graduations W of wet bulbtemperature, a ring 39 rotatable on the handle section and carrying ascale D of dry bulb temperatures at the edge adjacent the fixed ring 38and a scale RH of relative humidity at its opposite edge, and a secondfixed ring 40 carrying a fiducial mark 4% for cooperation with therelative humidity scale.

The psychrometer will usually be held in horizontal or approximatelyhorizontal position when the relative humidity of the air in the zone orspace is to be determined, but other angular arrangements of thepsychrometer are equally effective when the zone or space is limited andit is not convenient to employ the horizontal arrangement. The motorshould operate for a sufiicient period, according to the time-responsecharacteristics of the thermometers, to obtain stable minimum readings.The computer ring 39 is then adjusted to aline the observed readings onthe adjacent scales of the rings 38 and 39, and the relative humidityvalue appears on scale RH opposite the mark 4 l.

The accuracy of the determination of relative humidity depends of courseupon the accuracy of the measurement of the wet and dry bulbtemperatures. Air flow should be maintained for a preselected minimumperiod, and at a preselected minimum velocity, to obtain accuratetemperature readings. The velocity of the air streams varies with themotor speed, and this varies with the battery voltage. The centrifugalgovernor 2| and switch 19, 20 afford a positive indication or warningwhen the battery voltage drops to such value that the motor [5 can notdrive the fan 25 at such speed as to establish the desired minimum airflow velocity over the thermometer bulbs.

It is to be understood that the invention is not limited to theparticular embodiment herein illustrated and described since variousmodifications in the shape, size and relative arrange- 'ments of thecomponent parts fall within the spirit and scope of the invention as setforth in the following claims.

I claim:

1. In a motorized psychrometer, an elongated support comprising atubular handle portion of a diameter to be conveniently grasped in thehand and an outer section in axial alinement with and having atransverse cross-section of the order of that of the handle portion, awet and a dry bulb thermometer mounted on the outer section of saidsupport and parallel to the axis thereof, and power means forestablishing an air stream moving inwardly along said outer section ofsaid support upon which said thermometers are mounted; said power meanscomprising batteries within said tubular handle portion, an electricalmotor and fan at the outer end of said hollow handle portion of saidsupport, and an assembly comprising a sub-base supporting saidthermometers and a water reservoir, and means detachably securing saidassembly to said outer section of said elongated support; the bulb endsof said thermometers being located adjacent the inlet side of and in theair stream established by said fan.

2. In a motorized psychrometer, the invention as recited in claim 1,wherein a tubular section of said support extends over the bulb ends ofsaid thermometers to form a passage for the air stream established bysaid fan.

3. In a motorized psychrometer, the invention as recited in claim 2, incombination with means on said sub-base to provide separate air passagesover said wet bulb and said dry bulb thermometers.

4. In a motorized psychrometer, the invention as recited in claim 1,wherein said outer section of said elongated support is an approximatelysemi-cylindrical extension of said tubular handle portion, incombination with a sub-base of generally cruciform cross-section formedby metal strips at right angles, said sub-base being seated in saidouter section of said support;

said sub-base including a water reservoir, and

said thermometers being mounted on said subbase at opposite sides of astrip of said sub-base.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 275,222 Langenbach Apr. 3, 1883 1,234,529 Comins July 24, 19171,636,350 Armstrong July 19, 1927 2,089,627 Stephenson Aug. 10, 19372,251,623 Crofoot et al Aug. 5, 1941 2,264,966 Burdick et al. Dec. 2,1941 2,407,106 Shelly Sept. 3, 1946 FOREIGN PATENTS Number Country Date691,588 Germany Oct. 23, 1936 559,513 Great Britain Feb. 23, 1944241,697 Switzerland Aug. 1, 1946

